S23 is a potent investigational SARM (Selective Androgen Receptor Modulator) developed by GTx Inc., primarily researched for male hormonal contraception and muscle wasting disorders. Among SARMs, S23 stands out due to its high binding affinity to the androgen receptor and strong anabolic-to-androgenic ratio, making it popular in bodybuilding for muscle gain and cutting cycles—though it has never been approved for medical use.
Overview of S23
| Property | Details |
|---|---|
| Full Name | S-23 |
| Developer | GTx, Inc. |
| Molecular Formula | C18H13ClF4N2O3 |
| Class | SARM |
| Intended Use | Male contraception, muscle wasting |
| Half-life | ~12 hours (requires twice-daily dosing) |
| Administration | Oral (most common) |
Benefits for Bodybuilders
| Effect | Details |
|---|---|
| Lean Muscle Gain | Strong anabolic effects with hard, dry gains |
| Fat Loss | Promotes fat oxidation and a lean, vascular appearance |
| Muscle Hardness | Notably improves muscle density and definition |
| Non-Aromatising | Doesn’t convert to estrogen |
| Strength Increase | Notable gains in power and endurance |
Side Effects
Despite being a SARM (which generally have fewer side effects than steroids), S23 is considered the most suppressive of all SARMs.
| Possible Side Effect | Details |
|---|---|
| Testosterone Suppression | Severe suppression; PCT (Post Cycle Therapy) is essential |
| Aggression/Libido Changes | Increased aggression, libido fluctuation |
| Acne and Hair Shedding | Mild androgenic effects in susceptible users |
| Night Sweats | Frequently reported anecdotally |
| Dark Urine | Occasionally reported due to liver strain (though data is limited) |
Research Highlights
- Contraceptive Use: In rodent studies, S23 completely suppressed sperm production, with effects reversed after discontinuation.
- Anabolic Strength: Comparable or superior to testosterone in lean muscle tissue enhancement.
- Selective Binding: High affinity for androgen receptors in muscle and bone while sparing the prostate.
Comparison with Other SARMs
| SARM | Anabolic Strength | Suppression | Ideal Use |
|---|---|---|---|
| S23 | Very High | Very High | Cutting/Hardening |
| RAD-140 | High | Moderate | Bulking/Recomp |
| LGD-4033 | High | Moderate | Lean Bulking |
| MK-2866 | Mild | Low | Recomp/Therapeutic |
| YK-11 | Very High | High | Aggressive Bulking |
S23 Cycle Example (Not Medical Advice)
| Weeks | S23 Dose | Notes |
|---|---|---|
| 1–8 | 10–20 mg per day | Often split in 2 doses due to 12h half-life |
| 9–12 | PCT (e.g. Nolvadex, Clomid) | Crucial to restore testosterone |
✅ Summary
S23 is one of the most powerful SARMs in terms of muscle hardening and fat loss, often used in cutting cycles or pre-contest prep by bodybuilders. However, its strong testosterone suppression and lack of long-term safety data make it a high-risk compound, especially without proper PCT and monitoring.
Frequently Asked Questions (FAQ) – S23 (100x20mg Tablets)
Q1: What is S23?
A: S23 is a Selective Androgen Receptor Modulator (SARM) known for its powerful anabolic effects. It was developed to increase lean muscle mass and reduce body fat while offering better tissue selectivity than traditional anabolic steroids.
Q2: What does each tablet of S23 contain?
A: Each tablet contains 20mg of active S23 compound, typically sold in quantities of 100 tablets per pack.
Q3: How does S23 work in the body?
A: S23 binds selectively to androgen receptors in muscle and bone tissues. This promotes muscle hypertrophy and strength without significantly affecting prostate tissue or other androgen-sensitive organs.
Q4: Is S23 suppressive to natural testosterone?
A: Yes, S23 is highly suppressive. Users almost always require a proper Post Cycle Therapy (PCT) following a cycle to restart endogenous testosterone production.
Q5: What are the benefits of using S23?
A:
- Noticeable lean muscle gains
- Fat loss and muscle hardening
- Increased vascularity
- Enhanced endurance and strength
- Minimal water retention
Q6: What are the common dosages for S23?
A: Bodybuilders typically take 10-30mg per day, often split into two doses due to S23’s short half-life (around 12 hours). Beginners often start at 10mg daily.
Q7: How long should an S23 cycle last?
A: A typical cycle lasts 6 to 8 weeks. Due to its potency and suppressive nature, it’s not recommended to run it longer without medical supervision and a proper support plan.
Q8: Can S23 be stacked with other SARMs?
A: Yes. Common stacks include:
- S23 + RAD-140 (for strength and lean mass)
- S23 + MK-677 (to improve recovery and joint health)
- S23 + Cardarine (for cutting and endurance)
Q9: Does S23 convert to estrogen?
A: No, S23 does not aromatise into estrogen. However, some users report estrogen-like side effects due to suppression of natural testosterone and hormonal imbalance.
Q10: What are the side effects of S23?
A:
- Testosterone suppression
- Increased aggression or mood changes
- Night sweats
- Potential hair thinning (dose dependent)
- Risk of infertility during usage (shown in animal studies)
Q11: Is S23 liver toxic?
A: It is not C-17 alpha alkylated, so liver toxicity is relatively low. Still, using liver support supplements like TUDCA is advisable.
Q12: Do I need PCT after using S23?
A: Absolutely. S23 is one of the most suppressive SARMs and requires a robust PCT protocol. Clomid or Nolvadex is typically recommended.
Q13: Is S23 legal?
A: In most countries, S23 is not approved for human use and is sold as a research chemical. It is banned by WADA and most sports organisations.
Q14: Who should avoid S23?
A:
- Women (due to strong androgenic effects)
- Individuals with hormone-sensitive conditions
- Beginners unfamiliar with PCT
- Athletes subject to drug testing
Q15: What’s the shelf life of S23 tablets?
A: Most S23 products, if stored in a cool, dry place, are stable for 2-3 years from the date of manufacture.
Q16: Can S23 cause gyno (gynecomastia)?
A: While S23 doesn’t convert to estrogen, suppression of natural testosterone may increase estrogen dominance, leading to possible symptoms. An AI (Aromatase Inhibitor) may be needed post-cycle if symptoms arise.
Q17: Should I cycle S23 solo or stacked?
A: It can be used solo for cutting or recomp, but stacking with other SARMs or peptides may enhance results for experienced users. Always include PCT.
Q18: Can S23 be used for bulking?
A: While not typically a bulking SARM, S23 can assist in lean bulking when combined with a high-calorie diet and mass-promoting agents.
Q19: How quickly does S23 work?
A: Users report noticeable changes in strength and muscle hardness within 10–14 days, with fat loss and physique changes visible after 3–4 weeks.
Q20: Is S23 suitable for contest prep?
A: Yes. Due to its dry, hardening effect, it’s often used during the final 6 weeks leading to a show, especially when stacked with Cardarine or Stenabolic.
